Vehicle mass detection system

Abstract

A vehicle system and a method for calculating a vehicle mass is provided. In at least one embodiment, the system and the method measure current consumed by an electric machine of the vehicle to calculate vehicle mass. A controller of the vehicle uses the calculated mass to control operation of the vehicle, for example a four wheel drive, transmission, stability control, or brake system of the vehicle. A GPS and tire speed sensor system may be incorporated to detect the presence of a towed object, for example a trailer, and to further adjust operation of the vehicle.

What is claimed is: 
     
       1. A method of controlling an electric vehicle based on vehicle mass, the method comprising:
 providing at least a portion of vehicle propulsive torque with an electric machine; 
 while a speed of the electric machine is changing, measuring current consumed by the electric machine at two different instances of time; 
 calculating a mass of the vehicle based on the measured currents; and 
 controlling operation of the vehicle according to the calculated mass. 
 
     
     
       2. The method of  claim 1 , wherein the step of controlling comprises controlling at least one of a four wheel drive control system, transmission control system, stability control system, and a brakes system according to the calculated mass. 
     
     
       3. The method of  claim 1  further comprising maintaining a constant engine propulsive torque while the speed of the electric machine is changing. 
     
     
       4. The method of  claim 1  further comprising disconnecting an engine of the vehicle such that the engine provides no propulsive torque while the speed of the electric machine is changing. 
     
     
       5. The method of  claim 1  further comprising tracking a distance traveled by the vehicle and a number of tire revolutions of the vehicle for the distance traveled and comparing the distance traveled and the number of tire revolutions to stored data corresponding to a number of tire revolutions for the distance traveled at a given mass of the vehicle, wherein controlling operation of the vehicle according to the calculated mass includes adjusting operation of the vehicle according to the comparison. 
     
     
       6. The method of  5 , wherein the stored data further comprises data corresponding to a number of tire revolutions for the distance traveled at a plurality of vehicle masses. 
     
     
       7. The method of  claim 5  further comprising detecting a presence of a towed object attached to the vehicle based on at least one of the measured currents and the comparison. 
     
     
       8. The method of  claim 7 , wherein if no towed object is detected, a correction factor is created for the adjustment of the operation of the vehicle based on the measured currents. 
     
     
       9. A vehicle system comprising:
 an electric machine configured to provide a propulsive torque to the vehicle; and 
 at least one controller programmed to control operation of the vehicle based on current consumed by the electric machine at different instances of time while the vehicle is accelerating at least in part from the propulsive torque provided by the electric machine. 
 
     
     
       10. The system of  claim 9 , wherein the at least one controller is programmed to control at least one of a four wheel drive control system, transmission control system, stability control system, and a brakes system based on current consumed by the electric machine at different instances of time while the vehicle is accelerating. 
     
     
       11. The system of  claim 9  further comprising an engine configured to output a constant propulsive torque during and between the different instances of time while the vehicle is accelerating. 
     
     
       12. The system of  claim 9  further comprising an engine configured to output no propulsive torque during and between the different instances of time while the vehicle is accelerating. 
     
     
       13. The system of  claim 9  further comprising a global positioning system (GPS) in communication with the at least one controller and configured to track a distance traveled by the vehicle and at least one tire speed sensor configured to measure a number of tire revolutions of the vehicle for the distance traveled, wherein the at least one controller is further programmed to compare the distance traveled and the number of tire revolutions to stored data corresponding to a number of tire revolutions for the distance traveled at a given mass of the vehicle and to adjust operation of the vehicle based on the current consumed according to the comparison. 
     
     
       14. The system of  claim 13 , wherein the stored data further comprises data corresponding to a number of tire revolutions for the distance traveled at a plurality of vehicle masses. 
     
     
       15. The system of  claim 9 , wherein the at least one controller is further programmed to control operation of the vehicle based on current consumed by the electric machine at two different instances of time while the vehicle is accelerating. 
     
     
       16. The system of  claim 9 , wherein the at least one controller is further programmed to control operation of the vehicle based on current consumed by the electric machine at four different instances of time while the vehicle is accelerating.